The present invention relates to a plasma etching method using a plasma etching apparatus, and particularly to a method applicable to plasma etching on a multilayered film where a magnetic tunnel junction element is formed.
In recent years, a surface recording density is increasing rapidly by shifting from Giant Magneto Resistance (GMR) technology to Tunnel Magneto Resistance (TMR) technology in order to deal with a hard disk drive having a larger capacity. Accordingly, a magnetic head used for the hard disk drive is needed to be miniaturized, and microfabrication technology is demanded for the magnetic head. Therefore, application of an ion milling apparatus to a plasma etching apparatus is in progress for a magnetic head manufacturing device.
A magnetic head manufacturing method uses as a mask a photoresist formed by lithography similar to the semiconductor device and performs plasma etching to microfabricate a non-volatile material such as Al2O3; NiFe or Ru as well as a material such as SiO2, Ta or Cr often applied to the semiconductor device formed on a substrate.
In recent years, microfabrication makes it possible to reduce the linewidth of a material to be etched by reducing a photoresist, which is formed by lithography, by plasma etching before fabricating the material to be etched, and performing plasma etching on the material to be etched using the reduced mask pattern.
As a method of reducing the linewidth, for example, JP-A-9-237777 (corresponding to EP 0753885(A1)) discloses a method that a photoresist patterned by lithography is reduced by isotropic or partially isotropic etching to form a reduced linewidth patterned photoresist with a buried antireflection coating which functions as an etch stop or a dummy layer. The reduced linewidth pattern provides an etching mask for anisotropy etching that is subsequent to an underlying material such as polysilicon, metal, insulator or a ferroelectric substance.
JP-A-2001-196355 discloses a method that performs exposure and development of a photoresist film which is formed on an antireflection film made of an organic substance and etches the antireflection film with a mixed gas of Cl2, HBr, O2 and Ar. JP-A-10-98029 (corresponding to EP 0820093(A1)) discloses a method using a mixed gas of HBr and O2, and JP-A-2007-329505 discloses a method using a mixed gas of SO2 and He.